Alternating-current rectifying element



Patented Feb. 11, 1930 SAMUEL J. M. ALLEN, F CINCINNATI, OHIO ALTEBNATING-GURRENT REGTIFYING ELEMEN T No Drawing.

This invention relates to rectifying elements adapted to change an alternating electric current into a unidirectional current. The rectifying elements to which this invention is directed may be combined in series a or in parallel or in both to make up an alternating current rectifier of the desired capacity. 1

Each element comprises a copper oxide coating integrally formed on a cop er element disposed in an electric circuit Eetween two conductors. Such an elementshas the property of permitting an electric current to pass substantially in one direction only. The object of this invention is to provide a rectifying element of the class described, characterized by a low resistance in the direction of useful current flow.

A copper element, such as a plate two 29 inches in diameter and .30 of an inch thick is placed in an electric furnace, the temperature of which is about 1900 F. and is kept there for two to four minutes, at the end of which time the surface of the plate has acquired a coating of copper oxides. This plate when cooled has the property of per 1nitting current to flow from the copper oxide to the copper of the disk but not in the reverse direction to an appreciable ex- 30 tent. -In order to further lower the resistance of the plate in the useful direction and permit it to rectify a greater current in the useful direction, the plate is quenched at a temperature preferably between 1200 and 1300 F. though useful results are obtained at temperatures between 1000 and 1600 F.

This quenching is done in water, or similar inert liquids. After the plate has been quenched, the surface of the oxide coating may be treated to provide suitable electric contact as for example by being sand blasted and impressed with malleable foil, such as lead foil.

In all cases, the above described quench materially reduces the electrical resistance of the plate in the useful direction. These plates are then assembled into an alternating current rectifier, such as a battery charger which operates at a comparatively low temperature.

Having described my invention, I claim:

The process of reducing the electrical resistance in the useful direction of an electrical alternating current rectif ing element of the class described, comprising, the step of quenching a copper elementhaving a copper oxide coating thereon in an inert liquid when the element is at a temperature be- Application filed May 26, 1927. Serial No. 194,547.

tween 1200 degrees and 1300 degrees F.

my name.

SAMUEL J. M. ALLEN. 

